In order to reduce the cost of storing a large inventory, increasingly retailers and distributors rely upon systems that can rapidly receive wholesale quantities of particular articles and create subsets of different articles as consumer or store replenishment orders. In some instances, a large number of possible types of articles can be selected from to complete a particular order. Automation allows conveying selected articles from a receiving location, sorting the needed articles into an order container, and transporting the completed order container to a shipping location. Generally, human interaction is required along some portion of the otherwise automated material handling system.
AS/RS systems are designed for automated storing and retrieval of parts and items in manufacturing, distribution, retail, wholesale and institutions. They first originated in the 1960s, initially focusing on heavy pallet loads but with the evolution of the technology the handled loads have become smaller. The systems operate under computerized control, maintaining an inventory of stored items. Retrieval of items is accomplished by specifying the item type and quantity to be retrieved. The computer determines where in the storage area the item can be retrieved from and schedules the retrieval. It directs the proper automated storage and retrieval machine (SRM) to the location where the item is stored and directs the machine to deposit the item at a location where it is to be picked up. A system of conveyors and or automated guided vehicles, such as shuttles, are sometimes part of the AS/RS system. These take loads into and out of the storage area and move them to the manufacturing floor, loading docks, palletizer, or order fulfillment station. To store items, the pallet or tray is placed at an input station for the system, the information for inventory is entered into a computer terminal and the AS/RS system moves the load to the storage area, determines a suitable location for the item, and stores the load. As items are stored into or retrieved from the racks, the computer updates its inventory accordingly.
The benefits of an AS/RS system include reduced labor for transporting items into and out of inventory, reduced inventory levels, more accurate tracking of inventory, and space savings. Items are often stored more densely than in systems where items are stored and retrieved manually. The trend towards Just In Time production often requires sub-pallet level availability of production inputs, mixed pallet outputs, or e-commerce order fulfillment, and AS/RS is a much faster way of organizing the storage of smaller items next to production lines.
One AS/RS technology is known as shuttle technology. In this technology the horizontal movement is made by independent shuttles each operating on one level of a rack while a lift at a fixed position within the rack is responsible for the vertical movement. By using two separate machines for these two axes, the shuttle technology is able to provide higher throughput rates than stacker cranes and multi-level shuttles. Storage and Retrieval Machines pick up or drop off loads to the rest of the supporting transportation system at specific stations, where inbound and outbound loads are precisely positioned for proper handling.
Often the vertical lift can be the limiting item with regard to overall throughput of the AS/RS system. Each vertical lift is also a significant portion of the cost of overall AS/RS solution. Adding additional vertical lifts can make the resulting solution too expensive and with an insufficient return on investment to implement.